With the reduction in mortality due to combination antiretroviral therapy (cART), cardiovascular disease has emerged as a leading cause of death in HIV-infected patients. Because several antiretrovirals cause insulin resistance and dyslipidemia, the increased risk for atherosclerotic disease has been attributed primarily to these drugs. However, evidence is emerging that suggest untreated HIV infection contributes significantly to the risk for future cardiovascular events. Inflammation and endothelial cell dysfunction are key promoters of atherosclerosis in the general population. Vascular lesions in HIV-infected patients demonstrate increased leukocyte adhesion to the endothelium with elevated levels of monocyte chemoattractant protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1). In cART-nave patients, levels of these adhesion molecules are increased and endothelial dysfunction is common. cART only partly reduces levels of these molecules and only partly restores endothelial function. Our novel preliminary data suggest that the anti-inflammatory drug pentoxifylline (PTX) may significantly improve flow-mediated dilation of the brachial artery, an in vivo measure of endothelial function, in HIV-infected subjects by inhibiting leukocyte recruitment and adhesion. Using a cellular model, we found that HIV-infected T cells upregulate endothelial MCP-1 and that PTX inhibits endothelial production of MCP-1. We will directly address a specific objective of RFA-HL-08-003, which is to examine the direct effects of HIV itself on the endothelium and identify any mitigating factors in the proposed collaborative studies. In this application, we will address the central hypothesis that HIV-related inflammation induces endothelial cell dysfunction that is reversed with pentoxifylline. Our Specific Aims are (1) To determine the effects of pentoxifylline on endothelial function in HIV-infected subjects and (2) To analyze in vitro mechanisms by which HIV and PTX modulate endothelial cell activation and injury. We will investigate the utility of PTX to improve HIV-related endothelial dysfunction in therapeutic trials. We will also study the mechanism of HIV-induced endothelial dysfunction and the ability of PTX to reverse this process using our in vitro models. This research is both timely and significant because it will move beyond observational clinical research by involving both therapeutic trials and mechanistic investigations to identify novel causal relationships and pathologic mechanisms between inflammation and endothelial function. If pentoxifylline is found to be effective in improving endothelial function in the proposed studies, then this inexpensive, safe, and widely available drug can be studied in larger trials to reduce cardiovascular endpoints in HIV-infected patients.